Oxygenation of saturated aliphatic hydrocarbons



JULIUS M. NAIMAN AND HERBERT LEGGETT, F BLACKWELII,'OKL.AI'IOMA,Y SAID LEG- GETT ASSIGNOR TO SAID NAIMAN OXYGENATION OF SATURATED ALIPHAIIC HYDROGARBONS N0 Drawing.

Our invention relates to processes for producing hydroxides of hydrocarbons, and more particularly to such processes involving the use of pressure and a catalyst.

Our object is to provide an improved-process in this field, whereby convenient and reliable means for oxidizing a relatively plentiful gaseous hydrocarbon can be controlled to check oxidation at stages prior to the complete oxidation or" the hydrocarbon and prior to the dissociation of desired substances as produced by the process.

We accomplish our object by providing for the subjection of a mixture of a saturated aliphatic hydrocarbon and oxygen to temperature and pressure conditions adapted to our purpose, in the presence of a particular catalyzer, as will be more particularly described.

The problem we solve isbased on the premise that there is a combination of the hydrocarbon with oxygen preliminary to final combustion. Hydrocarbons combine with oxygen to form alcohols andaldehydes previous to, and as a preliminary, step in, burning to CO, CO and water. This holds true at all temperatures below the cracking points of the hydrocarbons. However, complete dissociation of the alcohols or aldehyd-es into CO and H occurs close to the ignition temperature, and as the temperature rises, the CO and H 0 combine with any additional oxygen present to form CO and H 0.

Evidently then, it only enough oxygen isv supplied to form, for example, methyl alco- 1 1101 from methane in accordance with the equation a CH O =CH OH for ethyl alcohol from ethane, viz.,

and some means were provided for preventing the alcohols from dissociating into CO and H in accordance with the equation a. CH OH; C0 2H and 1927. Serial No. 173,595.

dissociation of the methyl alcohol, CH OH into CO and H the extent of dissociation at different temperatures and pressures is important. If the rate of formation of CH OH is rapid enough at, say 1262 F. Abs, a pressure of 150 atmospheres will reduce the dissociation of alcohol to CO and H down to These and other considerations we have carefully studied theoretically and have reduced our conclusions to practice, with the result of our invention. 7

1We provide for an illustrative demonstration of our process means for supplyinga mixture of gases under compression, and a catalysis tube into which the mixture is ad mitted. I

The temperature in the catalysis tube is maintained within 10 of 325 F. (785 F. Abs). This is accomplished by providing a combination hot water-steam jacket around the catalysis tube. The water is at first heated until suflicient steam is generated to bring the steam to a pressure of 100# to 200:/:/:, the latter value being varied until the temperature of the air and the catalyzing materials in the catalysis tube reach the desired value of 325 F. The source of heat is then left temporarily on to offset radiation losses, and the proper methane-air mixture satisfying the proportions required by the equation filled with copper gauze and granulated zinc,

as one possible combination of catalyzing material, and this heated material being an excellent conductor of heat' quickly raises the temperature of the gas mixture to 325 F. The oxidation of methane then beginsto take place, tending to raise the temperature of the mixture above'325 F.

However, just as fast as heat is generated by the reaction, it is conducted away by the metallic catalyzing material through the catalysis tube wall to the water in the jacket. Then, because the external source of heat is removed, and because fresh water is slowly circulated through the jacket and the generated steam is allowed to escape from the jacket into a heat exchanger system, all heat conducted away by the catalyzer material to the tube walls is absorbed by the water and causes additional steam to begenerated.

By the proper control of water circulation and steam escapement, all the heat generated by the oxidation of the methane is absorbed by the water as fast as it is generated, with the result that such a more or less constant temperature is maintained in the steam-water jacket that the temperature inside the catalysis tube is maintained at a constant value of within 10 F. of 325 F.

The catalysis tube is so designed and the velocity of the'combustible mixture is so regulated that it takes the mixture between one and three seconds to pass through the catalyzing material. a

From the catalyzer, the gas-vapor mixture is conducted through cooling coils surrounded by circulating water, and leaves these coils at a temperature of about F. and enters a separator containing a large number of thin metallic rods depending two feet or more. The gas-vapor-liquid mixture enters at a point in the lower part of the separator and the mixture is forced to travel up two or more feet before it can leave the separator at the top, with the-result that all the liquid in the mixture is deposited on the forest of thinmetallic rods and carried down the latter to the bottom of the separator from where it is removed to a storage vat.

The gases and vapors after leaving the separator are then allowed to enter a second catalysis tube of practically the same construction as the first tube and are again heated by the catalyzer material to within 10 F. of 325 F., and any unoxidized methane is given another opportunity to be oxidized to methyl alcohol. ducted through a second bank of cooling coils to a second separator similar to the first one, where most of the remaining alcohol is re moved from the gases.

The gas-vapor mixture is allowed to leave the top of the second separatorthrough a long "vertical tube jacketed by a larger tube in such a manner that the gases upon leaving the first tube enter the annular space between this tube and the larger tube, this space being kept pressure tight. A valve is provided at the top of the smaller tube, and as the gas-vapor mixture passes through this valve it is allowed to suddenly expand from the 100 atmospheres pressure-to a lower pres sure, with the result that the heat lost due to adiabatic expansion lowers the temperature of the mixture to a predetermined low point,

causing every bit of'vapor to condense in the 'is allowed to pass.

The mixture is then con small tube and flow downward back into the second separator, down the metallic rods to the bottom of the separator, from where it is removed to the alcohol storage vat.

The cold gases consisting mostly of pure nitrogen are then allowed to leave the gas jacket and are circulated through coils located in-the same water cooler in which are located the cooling coils, through which the gas-vapor mixture leaving the catalysis tubes This makes it possible to maintain a low cooling water temperature without resorting to ice or a refrigerating plant. After leaving these cooling coils, the nitrogen and any other remaining gases are allowed to pass through a platinum sponge flame tester into the atmosphere. The size of the flame is found to be very small, and analysis of the waste gases shows an oxidation efficiency of 90 to j I The nitrogen, if the platinum sponge tester is left in continuous operation, is found to be about 99.5% pure and furnishes an excel lent possible raw material for a synthetic ammonia plant.

In the first plant, the methane and air mixture are compressed in the same compressor. The highest temperature reached in any of the compression cylindersis about 800 F. and the mixture is cooled down to about 150 F. between compression stages.

Maximum capacity in the particular demonstration related, is'limited by the maximum sized high pressure last stage cylinders which can be conveniently and economically built. By providing, however, for compressing the air and the natural gas separately and then bringing them'together in a suit: able mixer just before the mixture reaches the first catalysis tube, capacity may be increased.

'Analysis of the product shows a mixture of methyl, ethyl propyl and butyl alcohols, while an'analysis of the exhaust gases for eombustibles and specific gravity shows that practically all of theunoxidized combustibles in the exhaust gases consist of methane, so that practically all of the ethane, propane and butane of the natural gas are oxidized totheir respective alcohols, while most of the methane is oxidized to methyl alcohol;

When wet natural gas stripped of about 95% of its gasoline content by an absorption gasoline plant is used as a raw material, some 7 of the hexane and pentane 1n the stripped 1 1 gas remains in a vapor state, and some breaks up into CO and H finally escaping with the exhaust gases as a part of the combustible content of the exhaust gases.

Thus, since the hexane vapor-pressure at 32 F. is 0.9 lbs. per sq. in., stripped natural gas havin a residue hexane 'contentof .02 gallons per thousand cubic feet, would (on a basis of 1 gallon of hexane equals 30 cu. ft. 7

under atmospheric pressure and room temperature conditions), at 1500 lbs. pressure reach a vapor pressure of W: .090 lbs. per sqgallons of residue hexane per thousand cubic feet, before any of the hexane would begin to condense at 1500 lbs. pressure and 32 F. temperature. Since the actual temperature of the compressed gas is about 150 F. when it leaves the compressor, and about F. when it leaves the cooling coils, none of the residue hexane condenses out but escapes with the exhaust gases.

Similarly, if all the residue consisted of pentane, whose vapor pressure at 32 F. is 3.5 lbs. (P. Diserns, Recovery of Gasoline from Casinghead and Natural Gas Jour. Engineers Club of St. Louis, Jan.-Feb., 1918), then since the actual pressure of pentane at 1500 gas pressure would be as in the case of hexane, the stripped natural gas would have to contain .90 .02 .077 I gallons of residue pentane per thousand cubic feet, before any of the pentane would begin to condense at 1500 lbs. pressure and 32 F. temperature.

No tendency of the alcohols to dissociate into the original hydrocarbons occurs, so far as we have observed. 7

The method may be used for oxidizing gaseous hydrocarbons beyond the alcohol stage, viz., to formaldehyde, and other aldehydes, also into ketones, acids, etc., by using proper proportions of the hydrocarbons and air and by properly regulating the operating pressure and temperature, with pressure above 200 lb. gage and the temperature above the boiling pointof water.

What we claim and desire to secure by Letters Patent is:

1. The process of producing hydroxides of hydrocarbons including passing a gaseous =.909 lbs. per sq. in. i

. mixture containing free oxygen and saturated aliphatic hydrocarbons over a catalytic agent, maintaining the temperature of the catalytic agent at substantially 325 F., and maintaining pressure of the mixture at approximately 1500 pounds to prevent dissociation of the hydroxides formed. I

2. The process of producing hydroxides of gaseous hydrocarbons including passing a mixture of air saturated aliphatic hydrocarbons under a pressure of approximately 1500 pounds overa catalytic agent heated to approximately 325 F., and artificially re 7 moving heat generated due to oxidation of the hydrocarbons.

3. The process of producing hydroxidesof hydrocarbons by passing amixture of air and saturated aliphatic gaseous hydrocarbons under a pressure substantially 1500 pounds over a heated catalytic agent, externally cooling the agent to maintain the temperature thereof between 315 and 335 F., cooling the mixture, condensing compounds formed by the process, subjecting the remaining gas mixture to catalytic, cooling and condensing influences under conditions similar to those defined for the original mixture to provide a continuous process, and discharging the gases remaining after the final treatment.

4. In the process of producing a hydroxide of a saturated aliphatic gaseous hydrocarbon including passing a mixture consisting of the hydrocarbon and a free oxygen containing gas'over a heated catalyst, condensing the hydroxide and removing the remaining gases, the steps of applying pressure and controllin temperature proportionately in correspondence with application of a pressure of approximately 1500 pounds to the mixture and controlling the temperature of the mixtureat said pressure within 10, of

- 325 F., while the mixture is in contact with the catalyzer to control dissociation and combustion of the hydroxide.

5. In the process of producing a hydroxide of a gaseous hydrocarbon including passinga mixture consisting of a saturated aliphatic hydrocarbon and air over a heated catalyst, condensing the compounds and removing the remaining gases, the steps of ap plying pressure above 1500 lbs. to the mixture and controlling the temperature of the mixture to approximately 325 F. while the mixture is in contact with the catalyzer to com trol dissociation and combustion of the compounds and provide for discharge of substantially pure nitrogen gas from the system.

6. In the process of producing a hydroxide of a saturated aliphatic gaseous hydrocarbon including passing a mixture consisting of the hydrocarbon and free oxygen over a heated catalyst, condensing compounds formed by the process, and removing the remaining gases, the steps of applying pressure of approximately 1500 pounds to the mixture, and controlling the temperature of the mixture within 10 degrees of 325 F. when the mixture is in contact with. the catalyzer.

7 The process of controlling the produc-.

of the mixture While in contact with the catalytic agent to approximately 825 F. to cause the oxygen to combine with thehydrocarbon, applying pressure of approximately 1500 pounds to the mixture while subject to the influence of the catalytic agent to prevent dissociation, and condensing the hydroxide for discharging a gas mixture substantially free from oxygen from the system.

8. A process of the character described ineluding subjecting a mixture of free oxygen and saturated aliphatic gaseous hydrocarbons under pressure to the action of a catalyst at a controlled selected temperature above 315 F. for eilectin g reaction between the oxygen and the hydrocarbons to form hydroxides tending to dissociate at the selected tempera ture, and controlling said pressure to a value substantially proportionate to an approximate temperature of 325 F. and an approximate pressure of 1500 pounds to prevent dissociation of said hydroxides. V

" 9. A process of the character described wherein a mixture of free oxygen and a natura-l normally gaseous aliphatic hydrocarbon subjected to the action of catalyst in'the presence of heat above 315 F. tends to form hydroxides and the mixture'is contacted with the catalyst-under pressure for promoting the reaction, and wherein the mixture is contacted with the catalyst at a pressure substantially- 1500 pounds and approximately corresponding to the extent of elevation of the temperature above 315 F. i

10. The process of oxygenation of satu-V rated aliphatic gaseous hydrocarbons to produce an hydroxide including efiecting a mixture of a saturated aliphatic hydrocarbon and free oxygen, limiting the oxygen content of the mixture to an amount sufiicient to produce a desired oxygenated product,'passing the mixture under pressure over a catalyst, heating the catalyst to a temperature above 315 F. to effect reaction between the oxygen and the hydrocarbon to form hydroxides of the hydrocarbon, limiting the temperature of the catalyst below the cracking point of the hydrocarbon, controlling the pressure of the mixture while the mixture is in contact with the catalyst in direct proportion to the temperature of the catalyst in correspondence with a pressure of approximately 1500 pounds when the temperature of the catalyst isimaintained at approximately 325 F., condensing the hydroxide, and separating gas from the condensed hydroxide.

In testimony whereof we atfix our signai tures.

JULIUS M. NAIMAN. HERBERT LEGGETT. 

